Process:
(1) The precipitating factor causes a large number of hairs in anagen (synthesis) phase to prematurely enter telogen (resting) phase.
(2) Several weeks later the hair follicle enters into a new anagen phase, and the telogen hair is shed.
(3) Since a greater percentage of hairs are in telogen phase there is a greater percentage of hairs lost.
Groups of precipitating factors:
(1) endocrine or hormonal disorders
(2) nutritional disorders
(3) stress-related (physical or psychological)
(4) drug-induced
Endocrine or hormonal disorders:
(1) thyroid disorder (hyper or hypo)
(2) post-partum
(3) peri-menopausal or post-menopausal
(4) oral contraceptives
Nutritional disorders:
(1) protein malnutrition
(2) caloric malnutrition
(3) deficiency of essential fatty acids
(4) zinc deficiency
(5) biotin deficiency
(6) iron deficiency
(7) vitamin A intoxication
Stress-related:
(1) severe psychological stress
(2) after major surgery or trauma
(3) severe anemia
(4) after severe systemic illness
(5) after treatment in the ICU
Drug-induced:
(1) anticoagulants
(2) ACE (angiotensin converting enzyme) inhibitors
(3) antimitotic agent
(4) beta-blockers
(5) lithium
(6) retinoids
(7) valproic acid
No definite cause is found in some patients (idiopathic).
